The present invention relates to a process for manufacturing a silanized (meth)acrylate of formula: 
in which:
R represents hydrogen or methyl;
R1, R2 and R3 each independently represent a linear or branched C1-C10 alkyl radical, an aryl radical or an aralkyl radical, these radicals possibly being substituted and possibly containing hetero atoms.
The (meth)acrylates (I) are known for their use as hydrolysable monomers which serve for the preparation of binders in the field of self-smoothing antifouling marine paints intended, for example, for coating the hulls of boats or more generally of materials in contact with a marine environment (U.S. Pat. Nos. 4,593,055 and 4,687,792).
Various synthetic routes are described in the literature for manufacturing these silanized (meth)acrylates. These may be grouped in Table 1 below:
The synthetic routes described in Table 1 present, in one way or another, a number of drawbacks that the Applicant Company has succeeded in overcoming by carrying out the synthesis using (meth)acrylic anhydride and a silanized alkoxylated or hydroxylated derivative.
The process according to the invention for preparing the silanized (meth)acrylates (I) defined above allows them to be obtained under good conditions of conversion, selectivity and production efficiency, without waste products, without separation solids and without generation of H2. Thus, the manufacture of the silanized (meth)acrylates (I) according to the present invention may be carried out in total safety in simple stirred, heated stainless-steel reactors, in contrast with processes which generate H2 or HCl as by-products; in addition, it does not require any labour-intensive individual steps of the type such as filtration, washing or drying of solids.
A first subject of the present invention is thus a process for manufacturing a silanized (meth)acrylate of formula (I), as defined above, characterized in that the anhydride of formula (II): 
in which R is as defined above, is reacted with a silanized compound of formula (III) 
in which:
R1, R2 and R3 are as defined above; and
R4 represents hydrogen or a radical falling within the definition given above for R1, R2 and R3.
R1, R2, R3 and R4 are chosen especially from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl and alkylphenyl radicals with alkyl being C1-C10, R4 also possibly being hydrogen. R4 is preferably chosen from hydrogen, ethyl, n-propyl and n-butyl.
As indicated above, the radicals R1 to R3 may be substituted, for example, with halogen atoms, such as Cl or Br, or groups xe2x80x94NR5R6 (R5 and R6 representing C1 to C8 alkyl groups); moreover, the chain of these radicals may be interrupted with a hetero atom such as O or S.
The reaction of the invention is generally performed with a compound (II)/compound (III) molar ratio of between 0.3/1 and 3/1, although molar ratios of less than 0.3/1 or greater than 3/1 can theoretically be used. In accordance with one preferred embodiment of the invention, the reaction is performed with a compound (II)/compound (III) molar ratio of between 0.7/1 and 2/1 and preferably between 0.9/1 and 1.2/1.
The reaction is performed at a temperature of from 20 to 200xc2x0 C., preferably from 75 to 100xc2x0 C., in particular from 80 to 120xc2x0 C., and preferably at atmospheric pressure, although it is possible to perform the process under a pressure above or below atmospheric pressure.
Moreover, the reaction is performed to the point of maximum conversion of the reagents, determined using the usual analytical methods, for example such as gas chromatography. The reaction time depends on the operating conditions and on the reagents (II) and (III) used in the synthesis. It is generally between 3 and 8 hours.
The reaction (acylation) may be carried out with or without a catalyst. The use of a catalyst makes it possible to prevent the formation of disiloxanes, to increase the reaction kinetics and, as a result, to reduce the reaction time.
Among the catalysts which may be used, individually or as a mixture of two or more, mention may be made of 1-methylimidazole, dimethylaminopyridine, 4-pyrrolidinopyridine, 4-piperiditriflates, tributylphosphine, triethylamine, pyridine, montmorillonites such as montmorillonite K10 and KSF, protic acids such as para-toluenesulphonic acid and Lewis acids such as ZnCl2, the catalyst(s) generally being used in a proportion of from 0.05 to 1% by weight relative to the mixture of reagents. The use of larger amounts of catalyst is possible, although this does not provide an additional gain in terms of reducing the reaction time. 1-Methylimidazole is the preferred catalyst.
Moreover, the process according to the present invention is generally carried out in the presence of at least one polymerization inhibitor chosen especially from hydroquinone, hydroquinone methyl ether, phenothiazine, 2,2,5,5-tetramethyl-1-pyrrolidinyloxy (TEMPO) and homologues thereof such as 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy, 2,2,6,6-tetramethyl-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy and 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, and hindered phenolic inhibitors such as 2,4-dimethyl-6-tert-butylphenol and 2,6-di-tert-butyl-para-cresol, and homologues thereof, the polymerization inhibitors) being used in a proportion of from 0.05 to 0.5% by weight relative to the mixture of reagents.
The reaction according to the invention is advantageously carried out in the presence of air. The end of the reaction is determined by analysing the reaction medium (for example by GC).
The reaction according to the invention gives a crude mixture containing, besides compound (I), the compound of formula (IV) as a by-product: 
in which R and R4 are as defined in Claim 1, after which the said mixture may be freed of the lightest compounds by distillation (topping) or may be subjected, in order to obtain the pure compound (I), to a distillation, generally using a distillation column for the more volatile compounds (I) or a film evaporator for those with the highest boiling points.
The present invention also relates to the use of the crude mixture or of the mixture freed of the lightest compounds or of the pure compound (I), as obtained by the above process, as hydrolysable monomer(s) of a monomer composition whose polymerization gives a binder intended for self-smoothing antifouling marine paints. The binder is generally present in the paint composition in a proportion of from 10 to 30% by weight (in dry form).
The paint composition comprises the other usual ingredients, such as:
adjuvants, for instance soybean lecithin, modified hydrogenated castor oil or viscosity stabilizers (such as Viscostab CNF 896 manufactured by the company Atofina);
pigments and fillers, such as non-acicular zinc oxide, cuprous oxide and rutile titanium oxide; and
solvents and diluents such as the solvent naphtha, toluene and xylene.
The examples which follow illustrate the present invention without, however, limiting its scope. The percentages are expressed on a weight basis except where otherwise mentioned. The abbreviations used are as follows: